Interpretive Summary: Parasitic wasps are known to aid in controlling populations of pest ants and have been evaluated for their potential use against various invasive ant species (e.g., red imported fire ant). Certain tropical ants form nests in the canopies of citrus, oil, and coffee plantations often contributing to leaf loss or protecting plant-feeding insects (e.g. scales) attacking these crops. This can lead to losses in crop productivity costing millions of dollars annually. This paper reports a parasitic wasp that attacks a flower fly living in arboreal ant nests on citrus and oil plantations in Mexico. This is the first report documenting this family of parasitic wasp parasitizing a flower fly. This information will be useful to commodity growers, biocontrol workers, and ant ecologists.

Technical Abstract:
The host of Camponotophilus delvarei (Hymenoptera: Eurytomidae) is newly reported as Microdon sp. (Diptera: Syrphidae), a genus of obligatory myrmecophilous fly that predates ant brood, in this case Camponotus sp. aff. textor, in southern Mexico. The biology of Microdon spp. is reported as is that of C. delvarei. This is the first report of a eurytomid wasp as a primary parasitoid of a syrphid fly.